NAME

DESCRIPTION

This document describes differences between the 5.6.0 release and
the 5.8.0 release.

Many of the bug fixes in 5.8.0 were already seen in the 5.6.1
maintenance release since the two releases were kept closely
coordinated (while 5.8.0 was still called 5.7.something).

Changes that were integrated into the 5.6.1 release are marked [561]
.
Many of these changes have been further developed since 5.6.1 was released,
those are marked [561+]
.

You can see the list of changes in the 5.6.1 release (both from the
5.005_03 release and the 5.6.0 release) by reading perl561delta.

Highlights In 5.8.0

Better Unicode support

New IO Implementation

New Thread Implementation

Better Numeric Accuracy

Safe Signals

Many New Modules

More Extensive Regression Testing

Incompatible Changes

Binary Incompatibility

Perl 5.8 is not binary compatible with earlier releases of Perl.

You have to recompile your XS modules.

(Pure Perl modules should continue to work.)

The major reason for the discontinuity is the new IO architecture
called PerlIO. PerlIO is the default configuration because without
it many new features of Perl 5.8 cannot be used. In other words:
you just have to recompile your modules containing XS code, sorry
about that.

In future releases of Perl, non-PerlIO aware XS modules may become
completely unsupported. This shouldn't be too difficult for module
authors, however: PerlIO has been designed as a drop-in replacement
(at the source code level) for the stdio interface.

Depending on your platform, there are also other reasons why
we decided to break binary compatibility, please read on.

64-bit platforms and malloc

If your pointers are 64 bits wide, the Perl malloc is no longer being
used because it does not work well with 8-byte pointers. Also,
usually the system mallocs on such platforms are much better optimized
for such large memory models than the Perl malloc. Some memory-hungry
Perl applications like the PDL don't work well with Perl's malloc.
Finally, other applications than Perl (such as mod_perl) tend to prefer
the system malloc. Such platforms include Alpha and 64-bit HPPA,
MIPS, PPC, and Sparc.

AIX Dynaloading

The AIX dynaloading now uses in AIX releases 4.3 and newer the native
dlopen interface of AIX instead of the old emulated interface. This
change will probably break backward compatibility with compiled
modules. The change was made to make Perl more compliant with other
applications like mod_perl which are using the AIX native interface.

The myEXPR:ATTRS
syntax now applies variable attributes at
run-time. (Subroutine and our variables still get attributes applied
at compile-time.) See attributes for additional details. In particular,
however, this allows variable attributes to be useful for tie interfaces,
which was a deficiency of earlier releases. Note that the new semantics
doesn't work with the Attribute::Handlers module (as of version 0.76).

Socket Extension Dynamic in VMS

The Socket extension is now dynamically loaded instead of being
statically built in. This may or may not be a problem with ancient
TCP/IP stacks of VMS: we do not know since we weren't able to test
Perl in such configurations.

IEEE-format Floating Point Default on OpenVMS Alpha

Perl now uses IEEE format (T_FLOAT) as the default internal floating
point format on OpenVMS Alpha, potentially breaking binary compatibility
with external libraries or existing data. G_FLOAT is still available as
a configuration option. The default on VAX (D_FLOAT) has not changed.

Previously in Perl 5.6 to use Unicode one would say "use utf8" and
then the operations (like string concatenation) were Unicode-aware
in that lexical scope.

This was found to be an inconvenient interface, and in Perl 5.8 the
Unicode model has completely changed: now the "Unicodeness" is bound
to the data itself, and for most of the time "use utf8" is not needed
at all. The only remaining use of "use utf8" is when the Perl script
itself has been written in the UTF-8 encoding of Unicode. (UTF-8 has
not been made the default since there are many Perl scripts out there
that are using various national eight-bit character sets, which would
be illegal in UTF-8.)

See perluniintro for the explanation of the current model,
and utf8 for the current use of the utf8 pragma.

New Unicode Properties

Unicode scripts are now supported. Scripts are similar to (and superior
to) Unicode blocks. The difference between scripts and blocks is that
scripts are the glyphs used by a language or a group of languages, while
the blocks are more artificial groupings of (mostly) 256 characters based
on the Unicode numbering.

In general, scripts are more inclusive, but not universally so. For
example, while the script Latin
includes all the Latin characters and
their various diacritic-adorned versions, it does not include the various
punctuation or digits (since they are not solely Latin
).

A number of other properties are now supported, including \p{L&},
\p{Any}\p{Assigned}
, \p{Unassigned}
, \p{Blank}
[561] and
\p{SpacePerl}
[561] (along with their \P{...}
versions, of course).
See perlunicode for details, and more additions.

The In
or Is
prefix to names used with the \p{...}
and \P{...}
are now almost always optional. The only exception is that a In
prefix
is required to signify a Unicode block when a block name conflicts with a
script name. For example, \p{Tibetan}
refers to the script, while
\p{InTibetan}
refers to the block. When there is no name conflict, you
can omit the In
from the block name (e.g. \p{BraillePatterns}
), but
to be safe, it's probably best to always use the In
).

REF(...) Instead Of SCALAR(...)

A reference to a reference now stringifies as "REF(0x81485ec)" instead
of "SCALAR(0x81485ec)" in order to be more consistent with the return
value of ref().

pack/unpack D/F recycled

The undocumented pack/unpack template letters D/F have been recycled
for better use: now they stand for long double (if supported by the
platform) and NV (Perl internal floating point type). (They used
to be aliases for d/f, but you never knew that.)

glob() now returns filenames in alphabetical order

The list of filenames from glob() (or <...>) is now by default sorted
alphabetically to be csh-compliant (which is what happened before
in most Unix platforms). (bsd_glob() does still sort platform
natively, ASCII or EBCDIC, unless GLOB_ALPHASORT is specified.) [561]

Deprecations

The semantics of bless(REF, REF) were unclear and until someone proves
it to make some sense, it is forbidden.

The obsolete chat2 library that should never have been allowed
to escape the laboratory has been decommissioned.

Using chdir("") or chdir(undef) instead of explicit chdir() is
doubtful. A failure (think chdir(some_function()) can lead into
unintended chdir() to the home directory, therefore this behaviour
is deprecated.

The builtin dump() function has probably outlived most of its
usefulness. The core-dumping functionality will remain in future
available as an explicit call to CORE::dump()
, but in future
releases the behaviour of an unqualified dump() call may change.

The very dusty examples in the eg/ directory have been removed.
Suggestions for new shiny examples welcome but the main issue is that
the examples need to be documented, tested and (most importantly)
maintained.

The (bogus) escape sequences \8 and \9 now give an optional warning
("Unrecognized escape passed through"). There is no need to \-escape
any \w
character.

The *glob{FILEHANDLE} is deprecated, use *glob{IO} instead.

The package; syntax (package without an argument) has been
deprecated. Its semantics were never that clear and its
implementation even less so. If you have used that feature to
disallow all but fully qualified variables, usestrict;
instead.

The unimplemented POSIX regex features [[.cc.]] and [[=c=]] are still
recognised but now cause fatal errors. The previous behaviour of
ignoring them by default and warning if requested was unacceptable
since it, in a way, falsely promised that the features could be used.

In future releases, non-PerlIO aware XS modules may become completely
unsupported. Since PerlIO is a drop-in replacement for stdio at the
source code level, this shouldn't be that drastic a change.

Previous versions of perl and some readings of some sections of Camel
III implied that the :raw
"discipline" was the inverse of :crlf
.
Turning off "clrfness" is no longer enough to make a stream truly
binary. So the PerlIO :raw
layer (or "discipline", to use the Camel
book's older terminology) is now formally defined as being equivalent
to binmode(FH) - which is in turn defined as doing whatever is
necessary to pass each byte as-is without any translation. In
particular binmode(FH) - and hence :raw
- will now turn off both
CRLF and UTF-8 translation and remove other layers (e.g. :encoding())
which would modify byte stream.

The current user-visible implementation of pseudo-hashes (the weird
use of the first array element) is deprecated starting from Perl 5.8.0
and will be removed in Perl 5.10.0, and the feature will be
implemented differently. Not only is the current interface rather
ugly, but the current implementation slows down normal array and hash
use quite noticeably. The fields
pragma interface will remain
available. The restricted hashes interface is expected to
be the replacement interface (see Hash::Util). If your existing
programs depends on the underlying implementation, consider using
Class::PseudoHash from CPAN.

The syntaxes @a->[...]
and %h->{...}
have now been deprecated.

After years of trying, suidperl is considered to be too complex to
ever be considered truly secure. The suidperl functionality is likely
to be removed in a future release.

The 5.005 threads model (module Thread
) is deprecated and expected
to be removed in Perl 5.10. Multithreaded code should be migrated to
the new ithreads model (see threads, threads::shared and
perlthrtut).

The long deprecated uppercase aliases for the string comparison
operators (EQ, NE, LT, LE, GE, GT) have now been removed.

The tr///C and tr///U features have been removed and will not return;
the interface was a mistake. Sorry about that. For similar
functionality, see pack('U0', ...) and pack('C0', ...). [561]

Earlier Perls treated "sub foo (@bar)" as equivalent to "sub foo (@)".
The prototypes are now checked better at compile-time for invalid
syntax. An optional warning is generated ("Illegal character in
prototype...") but this may be upgraded to a fatal error in a future
release.

The execLIST
and systemLIST
operations now produce warnings on
tainted data and in some future release they will produce fatal errors.

Core Enhancements

Unicode Overhaul

Unicode in general should be now much more usable than in Perl 5.6.0
(or even in 5.6.1). Unicode can be used in hash keys, Unicode in
regular expressions should work now, Unicode in tr/// should work now,
Unicode in I/O should work now. See perluniintro for introduction
and perlunicode for details.

The Unicode Character Database coming with Perl has been upgraded
to Unicode 3.2.0. For more information, see http://www.unicode.org/ .
[561+] (5.6.1 has UCD 3.0.1.)

For developers interested in enhancing Perl's Unicode capabilities:
almost all the UCD files are included with the Perl distribution in
the lib/unicore subdirectory. The most notable omission, for space
considerations, is the Unihan database.

The properties \p{Blank} and \p{SpacePerl} have been added. "Blank" is like
C isblank(), that is, it contains only "horizontal whitespace" (the space
character is, the newline isn't), and the "SpacePerl" is the Unicode
equivalent of \s (\p{Space} isn't, since that includes the vertical
tabulator character, whereas \s doesn't.)

See "New Unicode Properties" earlier in this document for additional
information on changes with Unicode properties.

PerlIO is Now The Default

IO is now by default done via PerlIO rather than system's "stdio".
PerlIO allows "layers" to be "pushed" onto a file handle to alter the
handle's behaviour. Layers can be specified at open time via 3-arg
form of open:

The built-in layers are: unix (low level read/write), stdio (as in
previous Perls), perlio (re-implementation of stdio buffering in a
portable manner), crlf (does CRLF <=> "\n" translation as on Win32,
but available on any platform). A mmap layer may be available if
platform supports it (mostly Unixes).

Layers to be applied by default may be specified via the 'open' pragma.

If your environment variables (LC_ALL, LC_CTYPE, LANG) look like you
want to use UTF-8 (any of the variables match /utf-?8/i
), your
STDIN, STDOUT, STDERR handles and the default open layer (see open)
are marked as UTF-8. (This feature, like other new features that
combine Unicode and I/O, work only if you are using PerlIO, but that's
the default.)

Note that after this Perl really does assume that everything is UTF-8:
for example if some input handle is not, Perl will probably very soon
complain about the input data like this "Malformed UTF-8 ..." since
any old eight-bit data is not legal UTF-8.

Note for code authors: if you want to enable your users to use UTF-8
as their default encoding but in your code still have eight-bit I/O streams
(such as images or zip files), you need to explicitly open() or binmode()
with :bytes
(see open and binmode), or you
can just use binmode(FH) (nice for pre-5.8.0 backward compatibility).

ithreads

The new interpreter threads ("ithreads" for short) implementation of
multithreading, by Arthur Bergman, replaces the old "5.005 threads"
implementation. In the ithreads model any data sharing between
threads must be explicit, as opposed to the model where data sharing
was implicit. See threads and threads::shared, and
perlthrtut.

As a part of the ithreads implementation Perl will also use
any necessary and detectable reentrant libc interfaces.

Restricted Hashes

A restricted hash is restricted to a certain set of keys, no keys
outside the set can be added. Also individual keys can be restricted
so that the key cannot be deleted and the value cannot be changed.
No new syntax is involved: the Hash::Util module is the interface.

Safe Signals

Perl used to be fragile in that signals arriving at inopportune moments
could corrupt Perl's internal state. Now Perl postpones handling of
signals until it's safe (between opcodes).

This change may have surprising side effects because signals no longer
interrupt Perl instantly. Perl will now first finish whatever it was
doing, like finishing an internal operation (like sort()) or an
external operation (like an I/O operation), and only then look at any
arrived signals (and before starting the next operation). No more corrupt
internal state since the current operation is always finished first,
but the signal may take more time to get heard. Note that breaking
out from potentially blocking operations should still work, though.

Understanding of Numbers

In general a lot of fixing has happened in the area of Perl's
understanding of numbers, both integer and floating point. Since in
many systems the standard number parsing functions like strtoul()
and atof()
seem to have bugs, Perl tries to work around their
deficiencies. This results hopefully in more accurate numbers.

Perl now tries internally to use integer values in numeric conversions
and basic arithmetics (+ - * /) if the arguments are integers, and
tries also to keep the results stored internally as integers.
This change leads to often slightly faster and always less lossy
arithmetics. (Previously Perl always preferred floating point numbers
in its math.)

Arrays now always interpolate into double-quoted strings [561]

In double-quoted strings, arrays now interpolate, no matter what. The
behavior in earlier versions of perl 5 was that arrays would interpolate
into strings if the array had been mentioned before the string was
compiled, and otherwise Perl would raise a fatal compile-time error.
In versions 5.000 through 5.003, the error was

Literal @example now requires backslash

In versions 5.004_01 through 5.6.0, the error was

In string, @example now must be written as \@example

The idea here was to get people into the habit of writing
"fred\@example.com"
when they wanted a literal @
sign, just as
they have always written "Give me back my \$5"
when they wanted a
literal $
sign.

Starting with 5.6.1, when Perl now sees an @
sign in a
double-quoted string, it always attempts to interpolate an array,
regardless of whether or not the array has been used or declared
already. The fatal error has been downgraded to an optional warning:

Possible unintended interpolation of @example in string

This warns you that "fred@example.com"
is going to turn into
fred.com
if you don't backslash the @
.
See http://perl.plover.com/at-error.html for more details
about the history here.

Miscellaneous Changes

AUTOLOAD is now lvaluable, meaning that you can add the :lvalue attribute
to AUTOLOAD subroutines and you can assign to the AUTOLOAD return value.

The $Config{byteorder} (and corresponding BYTEORDER in config.h) was
previously wrong in platforms if sizeof(long) was 4, but sizeof(IV)
was 8. The byteorder was only sizeof(long) bytes long (1234 or 4321),
but now it is correctly sizeof(IV) bytes long, (12345678 or 87654321).
(This problem didn't affect Windows platforms.)

Also, $Config{byteorder} is now computed dynamically--this is more
robust with "fat binaries" where an executable image contains binaries
for more than one binary platform, and when cross-compiling.

perl -d:Module=arg,arg,arg now works (previously one couldn't pass
in multiple arguments.)

do followed by a bareword now ensures that this bareword isn't
a keyword (to avoid a bug where doq(foo.pl)
tried to call a
subroutine called q). This means that for example instead of
do format() you must write do&format()
.

The builtin dump() now gives an optional warning
dump() better written as CORE::dump(),
meaning that by default dump(...) is resolved as the builtin
dump() which dumps core and aborts, not as (possibly) user-defined
sub dump
. To call the latter, qualify the call as &dump(...)
.
(The whole dump() feature is to considered deprecated, and possibly
removed/changed in future releases.)

chomp() and chop() are now overridable. Note, however, that their
prototype (as given by prototype("CORE::chomp") is undefined,
because it cannot be expressed and therefore one cannot really write
replacements to override these builtins.

END blocks are now run even if you exit/die in a BEGIN block.
Internally, the execution of END blocks is now controlled by
PL_exit_flags & PERL_EXIT_DESTRUCT_END. This enables the new
behaviour for Perl embedders. This will default in 5.10. See
perlembed.

Formats now support zero-padded decimal fields.

Although "you shouldn't do that", it was possible to write code that
depends on Perl's hashed key order (Data::Dumper does this). The new
algorithm "One-at-a-Time" produces a different hashed key order.
More details are in Performance Enhancements.

lstat(FILEHANDLE) now gives a warning because the operation makes no sense.
In future releases this may become a fatal error.

Spurious syntax errors generated in certain situations, when glob()
caused File::Glob to be loaded for the first time, have been fixed. [561]

Lvalue subroutines can now return undef in list context. However,
the lvalue subroutine feature still remains experimental. [561+]

A lost warning "Can't declare ... dereference in my" has been
restored (Perl had it earlier but it became lost in later releases.)

A new special regular expression variable has been introduced:
$^N
, which contains the most-recently closed group (submatch).

noModule;
does not produce an error even if Module does not have an
unimport() method. This parallels the behavior of use vis-a-vis
import. [561]

The numerical comparison operators return undef if either operand
is a NaN. Previously the behaviour was unspecified.

our can now have an experimental optional attribute unique
that
affects how global variables are shared among multiple interpreters,
see our.

will print "bar foo\n". This feature helps in writing
internationalised software, and in general when the order
of the parameters can vary.

The (\&) prototype now works properly. [561]

prototype(\[$@%&]) is now available to implicitly create references
(useful for example if you want to emulate the tie() interface).

A new command-line option, -t
is available. It is the
little brother of -T
: instead of dying on taint violations,
lexical warnings are given. This is only meant as a temporary
debugging aid while securing the code of old legacy applications.
This is not a substitute for -T.

In other taint news, the execLIST
and systemLIST
have now been
considered too risky (think exec@ARGV
: it can start any program
with any arguments), and now the said forms cause a warning under
lexical warnings. You should carefully launder the arguments to
guarantee their validity. In future releases of Perl the forms will
become fatal errors so consider starting laundering now.

Tied hash interfaces are now required to have the EXISTS and DELETE
methods (either own or inherited).

If tr/// is just counting characters, it doesn't attempt to
modify its target.

untie() will now call an UNTIE() hook if it exists. See perltie
for details. [561]

The rules for allowing underscores (underbars) in numeric constants
have been relaxed and simplified: now you can have an underscore
simply between digits.

Rather than relying on C's argv[0] (which may not contain a full pathname)
where possible $^X is now set by asking the operating system.
(eg by reading /proc/self/exe on Linux, /proc/curproc/file on FreeBSD)

A new variable, ${^TAINT}
, indicates whether taint mode is enabled.

You can now override the readline() builtin, and this overrides also
the <FILEHANDLE> angle bracket operator.

The command-line options -s and -F are now recognized on the shebang
(#!) line.

Use of the /c match modifier without an accompanying /g modifier
elicits a new warning: Useof/c modifier is meaningless without /g
.

Use of /c in substitutions, even with /g, elicits
Useof /cmodifierismeaninglessins///
.

Support for the CLONE
special subroutine had been added.
With ithreads, when a new thread is created, all Perl data is cloned,
however non-Perl data cannot be cloned automatically. In CLONE
you
can do whatever you need to do, like for example handle the cloning of
non-Perl data, if necessary. CLONE
will be executed once for every
package that has it defined or inherited. It will be called in the
context of the new thread, so all modifications are made in the new area.

Both variables and routines can have attribute handlers. Handlers can
be specific to type (SCALAR, ARRAY, HASH, or CODE), or specific to the
exact compilation phase (BEGIN, CHECK, INIT, or END).
See Attribute::Handlers.

B::Concise
, by Stephen McCamant, is a new compiler backend for
walking the Perl syntax tree, printing concise info about ops.
The output is highly customisable. See B::Concise. [561+]

The new bignum, bigint, and bigrat pragmas, by Tels, implement
transparent bignum support (using the Math::BigInt, Math::BigFloat,
and Math::BigRat backends).

Class::ISA
, by Sean Burke, is a module for reporting the search
path for a class's ISA tree. See Class::ISA.

Cwd
now has a split personality: if possible, an XS extension is
used, (this will hopefully be faster, more secure, and more robust)
but if not possible, the familiar Perl implementation is used.

Devel::PPPort
, originally by Kenneth Albanowski and now
maintained by Paul Marquess, has been added. It is primarily used
by h2xs
to enhance portability of XS modules between different
versions of Perl. See Devel::PPPort.

Digest
, frontend module for calculating digests (checksums), from
Gisle Aas, has been added. See Digest.

Digest::MD5
for calculating MD5 digests (checksums) as defined in
RFC 1321, from Gisle Aas, has been added. See Digest::MD5.

Encode
, originally by Nick Ing-Simmons and now maintained by Dan
Kogai, provides a mechanism to translate between different character
encodings. Support for Unicode, ISO-8859-1, and ASCII are compiled in
to the module. Several other encodings (like the rest of the
ISO-8859, CP*/Win*, Mac, KOI8-R, three variants EBCDIC, Chinese,
Japanese, and Korean encodings) are included and can be loaded at
runtime. (For space considerations, the largest Chinese encodings
have been separated into their own CPAN module, Encode::HanExtra,
which Encode will use if available). See Encode.

Any encoding supported by Encode module is also available to the
":encoding()" layer if PerlIO is used.

Hash::Util
is the interface to the new restricted hashes
feature. (Implemented by Jeffrey Friedl, Nick Ing-Simmons, and
Michael Schwern.) See Hash::Util.

I18N::Langinfo
can be used to query locale information.
See I18N::Langinfo.

I18N::LangTags
, by Sean Burke, has functions for dealing with
RFC3066-style language tags. See I18N::LangTags.

ExtUtils::Constant
, by Nicholas Clark, is a new tool for extension
writers for generating XS code to import C header constants.
See ExtUtils::Constant.

Filter::Simple
, by Damian Conway, is an easy-to-use frontend to
Filter::Util::Call. See Filter::Simple.

List::Util
, by Graham Barr, is a selection of general-utility
list subroutines, such as sum(), min(), first(), and shuffle().
See List::Util.

Locale::Constants
, Locale::Country
, Locale::CurrencyLocale::Language
, and Locale::Script, by Neil Bowers, have
been added. They provide the codes for various locale standards, such
as "fr" for France, "usd" for US Dollar, and "ja" for Japanese.

Locale::Maketext
, by Sean Burke, is a localization framework. See
Locale::Maketext, and Locale::Maketext::TPJ13. The latter is an
article about software localization, originally published in The Perl
Journal #13, and republished here with kind permission.

Math::BigRat
for big rational numbers, to accompany Math::BigInt and
Math::BigFloat, from Tels. See Math::BigRat.

Memoize
can make your functions faster by trading space for time,
from Mark-Jason Dominus. See Memoize.

PerlIO::scalar
, by Nick Ing-Simmons, provides the implementation
of IO to "in memory" Perl scalars as discussed above. It also serves
as an example of a loadable PerlIO layer. Other future possibilities
include PerlIO::Array and PerlIO::Code. See PerlIO::scalar.

Storable
gives persistence to Perl data structures by allowing the
storage and retrieval of Perl data to and from files in a fast and
compact binary format. Because in effect Storable does serialisation
of Perl data structures, with it you can also clone deep, hierarchical
datastructures. Storable was originally created by Raphael Manfredi,
but it is now maintained by Abhijit Menon-Sen. Storable has been
enhanced to understand the two new hash features, Unicode keys and
restricted hashes. See Storable.

In addition to extract_delimited(), there are also extract_bracketed(),
extract_quotelike(), extract_codeblock(), extract_variable(),
extract_tagged(), extract_multiple(), gen_delimited_pat(), and
gen_extract_tagged(). With these, you can implement rather advanced
parsing algorithms. See Text::Balanced.

threads
, by Arthur Bergman, is an interface to interpreter threads.
Interpreter threads (ithreads) is the new thread model introduced in
Perl 5.6 but only available as an internal interface for extension
writers (and for Win32 Perl for fork() emulation). See threads,
threads::shared, and perlthrtut.

B::Deparse has been significantly enhanced by Robin Houston. It can
now deparse almost all of the standard test suite (so that the tests
still succeed). There is a make target "test.deparse" for trying this
out.

Carp now has better interface documentation, and the @CARP_NOT
interface has been added to get optional control over where errors
are reported independently of @ISA, by Ben Tilly.

Class::Struct can now define the classes in compile time.

Class::Struct now assigns the array/hash element if the accessor
is called with an array/hash element as the sole argument.

The return value of Cwd::fastcwd() is now tainted.

Data::Dumper now has an option to sort hashes.

Data::Dumper now has an option to dump code references
using B::Deparse.

DB_File now supports newer Berkeley DB versions, among
other improvements.

Devel::Peek now has an interface for the Perl memory statistics
(this works only if you are using perl's malloc, and if you have
compiled with debugging).

The English module can now be used without the infamous performance
hit by saying

(Assuming, of course, that you don't need the troublesome variables
$`
, $&
, or $'
.) Also, introduced @LAST_MATCH_START
and
@LAST_MATCH_END
English aliases for @-
and @+
.

ExtUtils::MakeMaker has been significantly cleaned up and fixed.
The enhanced version has also been backported to earlier releases
of Perl and submitted to CPAN so that the earlier releases can
enjoy the fixes.

The arguments of WriteMakefile() in Makefile.PL are now checked
for sanity much more carefully than before. This may cause new
warnings when modules are being installed. See ExtUtils::MakeMaker
for more details.

Fcntl, Socket, and Sys::Syslog have been rewritten by Nicholas Clark
to use the new-style constant dispatch section (see ExtUtils::Constant).
This means that they will be more robust and hopefully faster.

File::Find now chdir()s correctly when chasing symbolic links. [561]

File::Find now has pre- and post-processing callbacks. It also
correctly changes directories when chasing symbolic links. Callbacks
(naughtily) exiting with "next;" instead of "return;" now work.

File::Find is now (again) reentrant. It also has been made
more portable.

The warnings issued by File::Find now belong to their own category.
You can enable/disable them with use/no warnings 'File::Find';.

File::Glob::glob() has been renamed to File::Glob::bsd_glob()
because the name clashes with the builtin glob(). The older
name is still available for compatibility, but is deprecated. [561]

File::Glob now supports GLOB_LIMIT
constant to limit the size of
the returned list of filenames.

IPC::Open3 now allows the use of numeric file descriptors.

IO::Socket now has an atmark() method, which returns true if the socket
is positioned at the out-of-band mark. The method is also exportable
as a sockatmark() function.

IO::Socket::INET failed to open the specified port if the service name
was not known. It now correctly uses the supplied port number as is. [561]

IO::Socket::INET has support for the ReusePort option (if your
platform supports it). The Reuse option now has an alias, ReuseAddr.
For clarity, you may want to prefer ReuseAddr.

IO::Socket::INET now supports a value of zero for LocalPort
(usually meaning that the operating system will make one up.)

'use lib' now works identically to @INC. Removing directories
with 'no lib' now works.

Math::BigFloat and Math::BigInt have undergone a full rewrite by Tels.
They are now magnitudes faster, and they support various bignum
libraries such as GMP and PARI as their backends.

Math::Complex handles inf, NaN etc., better.

Net::Ping has been considerably enhanced by Rob Brown: multihoming is
now supported, Win32 functionality is better, there is now time
measuring functionality (optionally high-resolution using
Time::HiRes), and there is now "external" protocol which uses
Net::Ping::External module which runs your external ping utility and
parses the output. A version of Net::Ping::External is available in
CPAN.

Note that some of the Net::Ping tests are disabled when running
under the Perl distribution since one cannot assume one or more
of the following: enabled echo port at localhost, full Internet
connectivity, or sympathetic firewalls. You can set the environment
variable PERL_TEST_Net_Ping to "1" (one) before running the Perl test
suite to enable all the Net::Ping tests.

POSIX::sigaction() is now much more flexible and robust.
You can now install coderef handlers, 'DEFAULT', and 'IGNORE'
handlers, installing new handlers was not atomic.

In Safe, %INC
is now localised in a Safe compartment so that
use/require work.

In SDBM_File on dosish platforms, some keys went missing because of
lack of support for files with "holes". A workaround for the problem
has been added.

In Search::Dict one can now have a pre-processing hook for the
lines being searched.

The Shell module now has an OO interface.

In Sys::Syslog there is now a failover mechanism that will go
through alternative connection mechanisms until the message
is successfully logged.

The Test module has been significantly enhanced.

Time::Local::timelocal() does not handle fractional seconds anymore.
The rationale is that neither does localtime(), and timelocal() and
localtime() are supposed to be inverses of each other.

The vars pragma now supports declaring fully qualified variables.
(Something that our() does not and will not support.)

The utf8::
name space (as in the pragma) provides various
Perl-callable functions to provide low level access to Perl's
internal Unicode representation. At the moment only length()
has been implemented.

Utility Changes

Emacs perl mode (emacs/cperl-mode.el) has been updated to version
4.31.

emacs/e2ctags.pl is now much faster.

enc2xs
is a tool for people adding their own encodings to the
Encode module.

h2ph
now supports C trigraphs.

h2xs
now produces a template README.

h2xs
now uses Devel::PPPort
for better portability between
different versions of Perl.

h2xs
uses the new ExtUtils::Constant module
which will affect newly created extensions that define constants.
Since the new code is more correct (if you have two constants where the
first one is a prefix of the second one, the first constant never
got defined), less lossy (it uses integers for integer constant,
as opposed to the old code that used floating point numbers even for
integer constants), and slightly faster, you might want to consider
regenerating your extension code (the new scheme makes regenerating
easy). h2xs now also supports C trigraphs.

libnetcfg
has been added to configure libnet.

perlbug
is now much more robust. It also sends the bug report to
perl.org, not perl.com.

perlcc
has been rewritten and its user interface (that is,
command line) is much more like that of the Unix C compiler, cc.
(The perlbc tools has been removed. Use perlcc -B
instead.)
Note that perlcc is still considered very experimental and
unsupported. [561]

perlivp
is a new Installation Verification Procedure utility
for running any time after installing Perl.

piconv
is an implementation of the character conversion utility
iconv
, demonstrating the new Encode module.

perlpod has been rewritten to be clearer and to record the best
practices gathered over the years.

perlpodspec is a more formal specification of the pod format,
mainly of interest for writers of pod applications, not to
people writing in pod.

perlretut is a regular expression tutorial. [561+]

perlrequick is a regular expressions quick-start guide.
Yes, much quicker than perlretut. [561]

perltodo has been updated.

perltootc has been renamed as perltooc (to not to conflict
with perltoot in filesystems restricted to "8.3" names).

perluniintro is an introduction to using Unicode in Perl.
(perlunicode is more of a detailed reference and background
information)

perlutil explains the command line utilities packaged with the Perl
distribution. [561+]

The following platform-specific documents are available before
the installation as README.platform, and after the installation
as perlplatform:

perlaixperlamigaperlapolloperlbeosperlbs2000

perlceperlcygwinperldguxperldosperlepocperlfreebsdperlhpux

perlhurdperlirixperlmachtenperlmacosperlmintperlmpeix

perlnetwareperlos2perlos390perlplan9perlqnxperlsolaris

perltru64perlutsperlvmesaperlvmsperlvosperlwin32

These documents usually detail one or more of the following subjects:
configuring, building, testing, installing, and sometimes also using
Perl on the said platform.

Eastern Asian Perl users are now welcomed in their own languages:
README.jp (Japanese), README.ko (Korean), README.cn (simplified
Chinese) and README.tw (traditional Chinese), which are written in
normal pod but encoded in EUC-JP, EUC-KR, EUC-CN and Big5. These
will get installed as

perljpperlkoperlcnperltw

The documentation for the POSIX-BC platform is called "BS2000", to avoid
confusion with the Perl POSIX module.

The documentation for the WinCE platform is called perlce (README.ce
in the source code kit), to avoid confusion with the perlwin32
documentation on 8.3-restricted filesystems.

Performance Enhancements

map() could get pathologically slow when the result list it generates
is larger than the source list. The performance has been improved for
common scenarios. [561]

sort() is also fully reentrant, in the sense that the sort function
can itself call sort(). This did not work reliably in previous
releases. [561]

sort() has been changed to use primarily mergesort internally as
opposed to the earlier quicksort. For very small lists this may
result in slightly slower sorting times, but in general the speedup
should be at least 20%. Additional bonuses are that the worst case
behaviour of sort() is now better (in computer science terms it now
runs in time O(N log N), as opposed to quicksort's Theta(N**2)
worst-case run time behaviour), and that sort() is now stable
(meaning that elements with identical keys will stay ordered as they
were before the sort). See the sort pragma for information.

The story in more detail: suppose you want to serve yourself a little
slice of Pi.

@digits = (3,1,4,1,5,9);

A numerical sort of the digits will yield (1,1,3,4,5,9), as expected.
Which 1
comes first is hard to know, since one 1
looks pretty
much like any other. You can regard this as totally trivial,
or somewhat profound. However, if you just want to sort the even
digits ahead of the odd ones, then what will

yield? The only even digit, 4
, will come first. But how about
the odd numbers, which all compare equal? With the quicksort algorithm
used to implement Perl 5.6 and earlier, the order of ties is left up
to the sort. So, as you add more and more digits of Pi, the order
in which the sorted even and odd digits appear will change.
and, for sufficiently large slices of Pi, the quicksort algorithm
in Perl 5.8 won't return the same results even if reinvoked with the
same input. The justification for this rests with quicksort's
worst case behavior. If you run

(something you might approximate if you wanted to merge two sorted
arrays using sort), doubling $N doesn't just double the quicksort time,
it quadruples it. Quicksort has a worst case run time that can
grow like N**2, so-called quadratic behaviour, and it can happen
on patterns that may well arise in normal use. You won't notice this
for small arrays, but you will notice it with larger arrays,
and you may not live long enough for the sort to complete on arrays
of a million elements. So the 5.8 quicksort scrambles large arrays
before sorting them, as a statistical defence against quadratic behaviour.
But that means if you sort the same large array twice, ties may be
broken in different ways.

Because of the unpredictability of tie-breaking order, and the quadratic
worst-case behaviour, quicksort was almost replaced completely with
a stable mergesort. Stable means that ties are broken to preserve
the original order of appearance in the input array. So

will yield (4,3,1,1,5,9), guaranteed. The even and odd numbers
appear in the output in the same order they appeared in the input.
Mergesort has worst case O(N log N) behaviour, the best value
attainable. And, ironically, this mergesort does particularly
well where quicksort goes quadratic: mergesort sorts (1..$N, 1..$N)
in O(N) time. But quicksort was rescued at the last moment because
it is faster than mergesort on certain inputs and platforms.
For example, if you really don't care about the order of even
and odd digits, quicksort will run in O(N) time; it's very good
at sorting many repetitions of a small number of distinct elements.
The quicksort divide and conquer strategy works well on platforms
with relatively small, very fast, caches. Eventually, the problem gets
whittled down to one that fits in the cache, from which point it
benefits from the increased memory speed.

Quicksort was rescued by implementing a sort pragma to control aspects
of the sort. The stable subpragma forces stable behaviour,
regardless of algorithm. The _quicksort and _mergesort
subpragmas are heavy-handed ways to select the underlying implementation.
The leading _
is a reminder that these subpragmas may not survive
beyond 5.8. More appropriate mechanisms for selecting the implementation
exist, but they wouldn't have arrived in time to save quicksort.

Hashes now use Bob Jenkins "One-at-a-Time" hashing key algorithm
( http://burtleburtle.net/bob/hash/doobs.html ). This algorithm is
reasonably fast while producing a much better spread of values than
the old hashing algorithm (originally by Chris Torek, later tweaked by
Ilya Zakharevich). Hash values output from the algorithm on a hash of
all 3-char printable ASCII keys comes much closer to passing the
DIEHARD random number generation tests. According to perlbench, this
change has not affected the overall speed of Perl.

unshift() should now be noticeably faster.

Installation and Configuration Improvements

Generic Improvements

INSTALL now explains how you can configure Perl to use 64-bit
integers even on non-64-bit platforms.

Policy.sh policy change: if you are reusing a Policy.sh file
(see INSTALL) and you use Configure -Dprefix=/foo/bar and in the old
Policy $prefix eq $siteprefix and $prefix eq $vendorprefix, all of
them will now be changed to the new prefix, /foo/bar. (Previously
only $prefix changed.) If you do not like this new behaviour,
specify prefix, siteprefix, and vendorprefix explicitly.

A new optional location for Perl libraries, otherlibdirs, is available.
It can be used for example for vendor add-ons without disturbing Perl's
own library directories.

In many platforms, the vendor-supplied 'cc' is too stripped-down to
build Perl (basically, 'cc' doesn't do ANSI C). If this seems
to be the case and 'cc' does not seem to be the GNU C compiler
'gcc', an automatic attempt is made to find and use 'gcc' instead.

gcc needs to closely track the operating system release to avoid
build problems. If Configure finds that gcc was built for a different
operating system release than is running, it now gives a clearly visible
warning that there may be trouble ahead.

Since Perl 5.8 is not binary-compatible with previous releases
of Perl, Configure no longer suggests including the 5.005
modules in @INC.

Configure -S
can now run non-interactively. [561]

Configure support for pdp11-style memory models has been removed due
to obsolescence. [561]

configure.gnu now works with options with whitespace in them.

installperl now outputs everything to STDERR.

Because PerlIO is now the default on most platforms, "-perlio" doesn't
get appended to the $Config{archname} (also known as $^O) anymore.
Instead, if you explicitly choose not to use perlio (Configure command
line option -Uuseperlio), you will get "-stdio" appended.

Another change related to the architecture name is that "-64all"
(-Duse64bitall, or "maximally 64-bit") is appended only if your
pointers are 64 bits wide. (To be exact, the use64bitall is ignored.)

In AFS installations, one can configure the root of the AFS to be
somewhere else than the default /afs by using the Configure
parameter -Dafsroot=/some/where/else.

APPLLIB_EXP, a lesser-known configuration-time definition, has been
documented. It can be used to prepend site-specific directories
to Perl's default search path (@INC); see INSTALL for information.

The version of Berkeley DB used when the Perl (and, presumably, the
DB_File extension) was built is now available as
@Config{qw(db_version_major db_version_minor db_version_patch)}
from Perl and as DB_VERSION_MAJOR_CFGDB_VERSION_MINOR_CFGDB_VERSION_PATCH_CFG
from C.

Building Berkeley DB3 for compatibility modes for DB, NDBM, and ODBM
has been documented in INSTALL.

If you have CPAN access (either network or a local copy such as a
CD-ROM) you can during specify extra modules to Configure to build and
install with Perl using the -Dextras=... option. See INSTALL for
more details.

In addition to config.over, a new override file, config.arch, is
available. This file is supposed to be used by hints file writers
for architecture-wide changes (as opposed to config.over which is
for site-wide changes).

If your file system supports symbolic links, you can build Perl outside
of the source directory by

mkdir perl/build/directory

cd perl/build/directory

sh /path/to/perl/source/Configure -Dmksymlinks ...

This will create in perl/build/directory a tree of symbolic links
pointing to files in /path/to/perl/source. The original files are left
unaffected. After Configure has finished, you can just say

makealltest

and Perl will be built and tested, all in perl/build/directory.
[561]

For Perl developers, several new make targets for profiling
and debugging have been added; see perlhack.

Use of the gprof tool to profile Perl has been documented in
perlhack. There is a make target called "perl.gprof" for
generating a gprofiled Perl executable.

If you have GCC 3, there is a make target called "perl.gcov" for
creating a gcoved Perl executable for coverage analysis. See
perlhack.

If you are on IRIX or Tru64 platforms, new profiling/debugging options
have been added; see perlhack for more information about pixie and
Third Degree.

Guidelines of how to construct minimal Perl installations have
been added to INSTALL.

The Thread extension is now not built at all under ithreads
(Configure -Duseithreads
) because it wouldn't work anyway (the
Thread extension requires being Configured with -Duse5005threads
).

Note that the 5.005 threads are unsupported and deprecated: if you
have code written for the old threads you should migrate it to the
new ithreads model.

The Gconvert macro ($Config{d_Gconvert}) used by perl for stringifying
floating-point numbers is now more picky about using sprintf %.*g
rules for the conversion. Some platforms that used to use gcvt may
now resort to the slower sprintf.

The obsolete method of making a special (e.g., debugging) flavor
of perl by saying

The DYNIX/ptx platform (also known as dynixptx) is supported at or
near osvers 4.5.2.

EBCDIC platforms (z/OS (also known as OS/390), POSIX-BC, and VM/ESA)
have been regained. Many test suite tests still fail and the
co-existence of Unicode and EBCDIC isn't quite settled, but the
situation is much better than with Perl 5.6. See perlos390,
perlbs2000 (for POSIX-BC), and perlvmesa for more information.

Building perl with -Duseithreads or -Duse5005threads now works under
HP-UX 10.20 (previously it only worked under 10.30 or later). You will
need a thread library package installed. See README.hpux. [561]

Mac OS Classic is now supported in the mainstream source package
(MacPerl has of course been available since perl 5.004 but now the
source code bases of standard Perl and MacPerl have been synchronised)
[561]

Mac OS X (or Darwin) should now be able to build Perl even on HFS+
filesystems. (The case-insensitivity used to confuse the Perl build
process.)

NCR MP-RAS is now supported. [561]

All the NetBSD specific patches (except for the installation
specific ones) have been merged back to the main distribution.

All the OpenBSD specific patches (except for the installation
specific ones) have been merged back to the main distribution.

Perl has been tested with the GNU pth userlevel thread package
( http://www.gnu.org/software/pth/pth.html ). All thread tests
of Perl now work, but not without adding some yield()s to the tests,
so while pth (and other userlevel thread implementations) can be
considered to be "working" with Perl ithreads, keep in mind the
possible non-preemptability of the underlying thread implementation.

Stratus VOS is now supported using Perl's native build method
(Configure). This is the recommended method to build Perl on
VOS. The older methods, which build miniperl, are still
available. See perlvos. [561+]

z/OS (formerly known as OS/390, formerly known as MVS OE) now has
support for dynamic loading. This is not selected by default,
however, you must specify -Dusedl in the arguments of Configure. [561]

Selected Bug Fixes

Numerous memory leaks and uninitialized memory accesses have been
hunted down. Most importantly, anonymous subs used to leak quite
a bit. [561]

The autouse pragma didn't work for Multi::Part::Function::Names.

caller() could cause core dumps in certain situations. Carp was
sometimes affected by this problem. In particular, caller() now
returns a subroutine name of (unknown)
for subroutines that have
been removed from the symbol table.

chop(@list) in list context returned the characters chopped in
reverse order. This has been reversed to be in the right order. [561]

Configure no longer includes the DBM libraries (dbm, gdbm, db, ndbm)
when building the Perl binary. The only exception to this is SunOS 4.x,
which needs them. [561]

The behaviour of non-decimal but numeric string constants such as
"0x23" was platform-dependent: in some platforms that was seen as 35,
in some as 0, in some as a floating point number (don't ask). This
was caused by Perl's using the operating system libraries in a situation
where the result of the string to number conversion is undefined: now
Perl consistently handles such strings as zero in numeric contexts.

Several debugger fixes: exit code now reflects the script exit code,
condition "0"
now treated correctly, the d
command now checks
line number, $.
no longer gets corrupted, and all debugger output
now goes correctly to the socket if RemotePort is set. [561]

The debugger (perl5db.pl) has been modified to present a more
consistent commands interface, via (CommandSet=580). perl5db.t was
also added to test the changes, and as a placeholder for further tests.

The debugger has a new dumpDepth
option to control the maximum
depth to which nested structures are dumped. The x
command has
been extended so that xNEXPR
dumps out the value of EXPR to a
depth of at most N levels.

The debugger can now show lexical variables if you have the CPAN
module PadWalker installed.

The order of DESTROYs has been made more predictable.

Perl 5.6.0 could emit spurious warnings about redefinition of
dl_error() when statically building extensions into perl.
This has been corrected. [561]

As a side effect of this fix, tied hash interfaces must define
the EXISTS and DELETE methods.

mkdir() now ignores trailing slashes in the directory name,
as mandated by POSIX.

Some versions of glibc have a broken modfl(). This affects builds
with -Duselongdouble
. This version of Perl detects this brokenness
and has a workaround for it. The glibc release 2.2.2 is known to have
fixed the modfl() bug.

Modulus of unsigned numbers now works (4063328477 % 65535 used to
return 27406, instead of 27047). [561]

Some "not a number" warnings introduced in 5.6.0 eliminated to be
more compatible with 5.005. Infinity is now recognised as a number. [561]

Numeric conversions did not recognize changes in the string value
properly in certain circumstances. [561]

Attributes (such as :shared) didn't work with our().

our() variables will not cause bogus "Variable will not stay shared"
warnings. [561]

"our" variables of the same name declared in two sibling blocks
resulted in bogus warnings about "redeclaration" of the variables.
The problem has been corrected. [561]

pack "Z" now correctly terminates the string with "\0".

Fix password routines which in some shadow password platforms
(e.g. HP-UX) caused getpwent() to return every other entry.

The PERL5OPT environment variable (for passing command line arguments
to Perl) didn't work for more than a single group of options. [561]

PERL5OPT with embedded spaces didn't work.

printf() no longer resets the numeric locale to "C".

qw(a\\b) now parses correctly as 'a\\b'
: that is, as three
characters, not four. [561]

pos() did not return the correct value within s///ge in earlier
versions. This is now handled correctly. [561]

Printing quads (64-bit integers) with printf/sprintf now works
without the q L ll prefixes (assuming you are on a quad-capable platform).

Regular expressions on references and overloaded scalars now work. [561+]

Right-hand side magic (GMAGIC) could in many cases such as string
concatenation be invoked too many times.

scalar() now forces scalar context even when used in void context.

SOCKS support is now much more robust.

sort() arguments are now compiled in the right wantarray context
(they were accidentally using the context of the sort() itself).
The comparison block is now run in scalar context, and the arguments
to be sorted are always provided list context. [561]

Changed the POSIX character class [[:space:]] to include the (very
rarely used) vertical tab character. Added a new POSIX-ish character
class [[:blank:]] which stands for horizontal whitespace
(currently, the space and the tab).

The tainting behaviour of sprintf() has been rationalized. It does
not taint the result of floating point formats anymore, making the
behaviour consistent with that of string interpolation. [561]

Some cases of inconsistent taint propagation (such as within hash
values) have been fixed.

The RE engine found in Perl 5.6.0 accidentally pessimised certain kinds
of simple pattern matches. These are now handled better. [561]

Multi-line matches like "a\nxb\n" =~ /(?!\A)x/m
were flawed. The
bug has been fixed. [561]

Use of $& could trigger a core dump under some situations. This
is now avoided. [561]

The regular expression captured submatches ($1, $2, ...) are now
more consistently unset if the match fails, instead of leaving false
data lying around in them. [561]

readline() on files opened in "slurp" mode could return an extra
"" (blank line) at the end in certain situations. This has been
corrected. [561]

Autovivification of symbolic references of special variables described
in perlvar (as in ${$num}
) was accidentally disabled. This works
again now. [561]

Sys::Syslog ignored the LOG_AUTH
constant.

$AUTOLOAD, sort(), lock(), and spawning subprocesses
in multiple threads simultaneously are now thread-safe.

Tie::Array's SPLICE method was broken.

Allow a read-only string on the left-hand side of a non-modifying tr///.

If STDERR
is tied, warnings caused by warn and die now
correctly pass to it.

Several Unicode fixes.

BOMs (byte order marks) at the beginning of Perl files
(scripts, modules) should now be transparently skipped.
UTF-16 and UCS-2 encoded Perl files should now be read correctly.

The character tables have been updated to Unicode 3.2.0.

Comparing with utf8 data does not magically upgrade non-utf8 data
into utf8. (This was a problem for example if you were mixing data
from I/O and Unicode data: your output might have got magically encoded
as UTF-8.)

Generating illegal Unicode code points such as U+FFFE, or the UTF-16
surrogates, now also generates an optional warning.

Compilation of the standard Perl distribution in Mac OS Classic should
now work if you have the Metrowerks development environment and the
missing Mac-specific toolkit bits. Contact the macperl mailing list
for details.

The operating system version letter now recorded in $Config{osvers}.
Allow compiling with gcc (previously explicitly forbidden). Compiling
with gcc still not recommended because buggy code results, even with
gcc 2.95.2.

Unicos

Fixed various alignment problems that lead into core dumps either
during build or later; no longer dies on math errors at runtime;
now using full quad integers (64 bits), previously was using
only 46 bit integers for speed.

chdir() now works better despite a CRT bug; now works with MULTIPLICITY
(see INSTALL); now works with Perl's malloc.

The tainting of %ENV
elements via keys or values was previously
unimplemented. It now works as documented.

The waitpid emulation has been improved. The worst bug (now fixed)
was that a pid of -1 would cause a wildcard search of all processes on
the system.

POSIX-style signals are now emulated much better on VMS versions prior
to 7.0.

The system function and backticks operator have improved
functionality and better error handling. [561]

File access tests now use current process privileges rather than the
user's default privileges, which could sometimes result in a mismatch
between reported access and actual access. This improvement is only
available on VMS v6.0 and later.

There is a new kill implementation based on sys$sigprc
that allows
older VMS systems (pre-7.0) to use kill to send signals rather than
simply force exit. This implementation also allows later systems to
call kill from within a signal handler.

Iterative logical name translations are now limited to 10 iterations in
imitation of SHOW LOGICAL and other OpenVMS facilities.

Windows

Signal handling now works better than it used to. It is now implemented
using a Windows message loop, and is therefore less prone to random
crashes.

fork() emulation is now more robust, but still continues to have a few
esoteric bugs and caveats. See perlfork for details. [561+]

A failed (pseudo)fork now returns undef and sets errno to EAGAIN. [561]

The following modules now work on Windows:

ExtUtils::Embed[561]

IO::Pipe

IO::Poll

Net::Ping

IO::File::new_tmpfile() is no longer limited to 32767 invocations
per-process.

Better chdir() return value for a non-existent directory.

Compiling perl using the 64-bit Platform SDK tools is now supported.

The Win32::SetChildShowWindow() builtin can be used to control the
visibility of windows created by child processes. See Win32 for
details.

The behavior of system() with multiple arguments has been rationalized.
Each unquoted argument will be automatically quoted to protect whitespace,
and any existing whitespace in the arguments will be preserved. This
improves the portability of system(@args) by avoiding the need for
Windows cmd
shell specific quoting in perl programs.

Note that this means that some scripts that may have relied on earlier
buggy behavior may no longer work correctly. For example,
system("nmake /nologo",@args)
will now attempt to run the file
nmake /nologo
and will fail when such a file isn't found.
On the other hand, perl will now execute code such as
system("c:/Program Files/MyApp/foo.exe",@args)
correctly.

The perl header files no longer suppress common warnings from the
Microsoft Visual C++ compiler. This means that additional warnings may
now show up when compiling XS code.

Borland C++ v5.5 is now a supported compiler that can build Perl.
However, the generated binaries continue to be incompatible with those
generated by the other supported compilers (GCC and Visual C++). [561]

Duping socket handles with open(F, ">&MYSOCK") now works under Windows 9x.
[561]

Current directory entries in %ENV are now correctly propagated to child
processes. [561]

New %ENV entries now propagate to subprocesses. [561]

Win32::GetCwd() correctly returns C:\ instead of C: when at the drive root.
Other bugs in chdir() and Cwd::cwd() have also been fixed. [561]

The makefiles now default to the features enabled in ActiveState ActivePerl
(a popular Win32 binary distribution). [561]

HTML files will now be installed in c:\perl\html instead of
c:\perl\lib\pod\html

REG_EXPAND_SZ keys are now allowed in registry settings used by perl. [561]

Can now send() from all threads, not just the first one. [561]

ExtUtils::MakeMaker now uses $ENV{LIB} to search for libraries. [561]

Less stack reserved per thread so that more threads can run
concurrently. (Still 16M per thread.) [561]

File::Spec->tmpdir()
now prefers C:/temp over /tmp
(works better when perl is running as service).

New or Changed Diagnostics

Ambiguous range in the transliteration operator (like a-z-9) now
gives a warning.

chdir("") and chdir(undef) now give a deprecation warning because they
cause a possible unintentional chdir to the home directory.
Say chdir() if you really mean that.

Two new debugging options have been added: if you have compiled your
Perl with debugging, you can use the -DT [561] and -DR options to trace
tokenising and to add reference counts to displaying variables,
respectively.

The lexical warnings category "deprecated" is no longer a sub-category
of the "syntax" category. It is now a top-level category in its own
right.

Unadorned dump() will now give a warning suggesting to
use explicit CORE::dump() if that's what really is meant.

The "Unrecognized escape" warning has been extended to include \8
,
\9
, and \_
. There is no need to escape any of the \w
characters.

All regular expression compilation error messages are now hopefully
easier to understand both because the error message now comes before
the failed regex and because the point of failure is now clearly
marked by a <-- HERE
marker.

Various I/O (and socket) functions like binmode(), close(), and so
forth now more consistently warn if they are used illogically either
on a yet unopened or on an already closed filehandle (or socket).

Using lstat() on a filehandle now gives a warning. (It's a non-sensical
thing to do.)

The -M
and -m options now warn if you didn't supply the module name.

If you in use specify a required minimum version, modules matching
the name and but not defining a $VERSION will cause a fatal failure.

Using negative offset for vec() in lvalue context is now a warnable offense.

Odd number of arguments to overload::constant now elicits a warning.

Odd number of elements in anonymous hash now elicits a warning.

The various "opened only for", "on closed", "never opened" warnings
drop the main::
prefix for filehandles in the main
package,
for example STDIN
instead of main::STDIN
.

Subroutine prototypes are now checked more carefully, you may
get warnings for example if you have used non-prototype characters.

If an attempt to use a (non-blessed) reference as an array index
is made, a warning is given.

push@a;
and unshift@a;
(with no values to push or unshift)
now give a warning. This may be a problem for generated and eval'ed
code.

If you try to pack a number less than 0 or larger than 255
using the "C"
format you will get an optional warning. Similarly
for the "c"
format and a number less than -128 or more than 127.

pack P
format now demands an explicit size.

unpack w
now warns of unterminated compressed integers.

Warnings relating to the use of PerlIO have been added.

Certain regex modifiers such as (?o) make sense only if applied to
the entire regex. You will get an optional warning if you try to do
otherwise.

Variable length lookbehind has not yet been implemented, trying to
use it will tell that.

Using arrays or hashes as references (e.g. %foo->{bar}
has been deprecated for a while. Now you will get an optional warning.

Warnings relating to the use of the new restricted hashes feature
have been added.

Self-ties of arrays and hashes are not supported and fatal errors
will happen even at an attempt to do so.

Using sort in scalar context now issues an optional warning.
This didn't do anything useful, as the sort was not performed.

Using the /g modifier in split() is meaningless and will cause a warning.

Using splice() past the end of an array now causes a warning.

Malformed Unicode encodings (UTF-8 and UTF-16) cause a lot of warnings,
as does trying to use UTF-16 surrogates (which are unimplemented).

Trying to use Unicode characters on an I/O stream without marking the
stream's encoding (using open() or binmode()) will cause "Wide character"
warnings.

Use of v-strings in use/require causes a (backward) portability warning.

Warnings relating to the use interpreter threads and their shared data
have been added.

Changed Internals

PerlIO is now the default.

perlapi.pod (a companion to perlguts) now attempts to document the
internal API.

You can now build a really minimal perl called microperl.
Building microperl does not require even running Configure;
make -f Makefile.micro
should be enough. Beware: microperl makes
many assumptions, some of which may be too bold; the resulting
executable may crash or otherwise misbehave in wondrous ways.
For careful hackers only.

Added rsignal(), whichsig(), do_join(), op_clear, op_null,
ptr_table_clear(), ptr_table_free(), sv_setref_uv(), and several UTF-8
interfaces to the publicised API. For the full list of the available
APIs see perlapi.

Made possible to propagate customised exceptions via croak()ing.

Now xsubs can have attributes just like subs. (Well, at least the
built-in attributes.)

dTHR and djSP have been obsoleted; the former removed (because it's
a no-op) and the latter replaced with dSP.

The regex compiler now maintains a structure that identifies nodes in
the compiled bytecode with the corresponding syntactic features of the
original regex expression. The information is attached to the new
offsets
member of the structregexp
. See perldebguts for more
complete information.

The C code has been made much more gcc -Wall
clean. Some warning
messages still remain in some platforms, so if you are compiling with
gcc you may see some warnings about dubious practices. The warnings
are being worked on.

perly.c, sv.c, and sv.h have now been extensively commented.

Documentation on how to use the Perl source repository has been added
to Porting/repository.pod.

There are now several profiling make targets.

Security Vulnerability Closed [561]

(This change was already made in 5.7.0 but bears repeating here.)
(5.7.0 came out before 5.6.1: the development branch 5.7 released
earlier than the maintenance branch 5.6)

A potential security vulnerability in the optional suidperl component
of Perl was identified in August 2000. suidperl is neither built nor
installed by default. As of November 2001 the only known vulnerable
platform is Linux, most likely all Linux distributions. CERT and
various vendors and distributors have been alerted about the vulnerability.
See http://www.cpan.org/src/5.0/sperl-2000-08-05/sperl-2000-08-05.txt
for more information.

The problem was caused by Perl trying to report a suspected security
exploit attempt using an external program, /bin/mail. On Linux
platforms the /bin/mail program had an undocumented feature which
when combined with suidperl gave access to a root shell, resulting in
a serious compromise instead of reporting the exploit attempt. If you
don't have /bin/mail, or if you have 'safe setuid scripts', or if
suidperl is not installed, you are safe.

The exploit attempt reporting feature has been completely removed from
Perl 5.8.0 (and the maintenance release 5.6.1, and it was removed also
from all the Perl 5.7 releases), so that particular vulnerability
isn't there anymore. However, further security vulnerabilities are,
unfortunately, always possible. The suidperl functionality is most
probably going to be removed in Perl 5.10. In any case, suidperl
should only be used by security experts who know exactly what they are
doing and why they are using suidperl instead of some other solution
such as sudo ( see http://www.courtesan.com/sudo/ ).

New Tests

Several new tests have been added, especially for the lib and
ext subsections. There are now about 69 000 individual tests
(spread over about 700 test scripts), in the regression suite (5.6.1
has about 11 700 tests, in 258 test scripts) The exact numbers depend
on the platform and Perl configuration used. Many of the new tests
are of course introduced by the new modules, but still in general Perl
is now more thoroughly tested.

Because of the large number of tests, running the regression suite
will take considerably longer time than it used to: expect the suite
to take up to 4-5 times longer to run than in perl 5.6. On a really
fast machine you can hope to finish the suite in about 6-8 minutes
(wallclock time).

The tests are now reported in a different order than in earlier Perls.
(This happens because the test scripts from under t/lib have been moved
to be closer to the library/extension they are testing.)

Known Problems

The Compiler Suite Is Still Very Experimental

The compiler suite is slowly getting better but it continues to be
highly experimental. Use in production environments is discouraged.

Localising Tied Arrays and Hashes Is Broken

doesn't work as one would expect: the old value is restored
incorrectly. This will be changed in a future release, but we don't
know yet what the new semantics will exactly be. In any case, the
change will break existing code that relies on the current
(ill-defined) semantics, so just avoid doing this in general.

Building Extensions Can Fail Because Of Largefiles

Some extensions like mod_perl are known to have issues with
`largefiles', a change brought by Perl 5.6.0 in which file offsets
default to 64 bits wide, where supported. Modules may fail to compile
at all, or they may compile and work incorrectly. Currently, there
is no good solution for the problem, but Configure now provides
appropriate non-largefile ccflags, ldflags, libswanted, and libs
in the %Config hash (e.g., $Config{ccflags_nolargefiles}) so the
extensions that are having problems can try configuring themselves
without the largefileness. This is admittedly not a clean solution,
and the solution may not even work at all. One potential failure is
whether one can (or, if one can, whether it's a good idea to) link
together at all binaries with different ideas about file offsets;
all this is platform-dependent.

Modifying $_ Inside for(..)

for (1..5){$_++ }

works without complaint. It shouldn't. (You should be able to
modify only lvalue elements inside the loops.) You can see the
correct behaviour by replacing the 1..5 with 1, 2, 3, 4, 5.

mod_perl 1.26 Doesn't Build With Threaded Perl

Use mod_perl 1.27 or higher.

lib/ftmp-security tests warn 'system possibly insecure'

Don't panic. Read the 'make test' section of INSTALL instead.

libwww-perl (LWP) fails base/date #51

Use libwww-perl 5.65 or later.

PDL failing some tests

Use PDL 2.3.4 or later.

Perl_get_sv

You may get errors like 'Undefined symbol "Perl_get_sv"' or "can't
resolve symbol 'Perl_get_sv'", or the symbol may be "Perl_sv_2pv".
This probably means that you are trying to use an older shared Perl
library (or extensions linked with such) with Perl 5.8.0 executable.
Perl used to have such a subroutine, but that is no more the case.
Check your shared library path, and any shared Perl libraries in those
directories.

Self-tying Problems

Self-tying of arrays and hashes is broken in rather deep and
hard-to-fix ways. As a stop-gap measure to avoid people from getting
frustrated at the mysterious results (core dumps, most often), it is
forbidden for now (you will get a fatal error even from an attempt).

A change to self-tying of globs has caused them to be recursively
referenced (see: Two-Phased Garbage Collection in perlobj). You
will now need an explicit untie to destroy a self-tied glob. This
behaviour may be fixed at a later date.

Self-tying of scalars and IO thingies works.

ext/threads/t/libc

If this test fails, it indicates that your libc (C library) is not
threadsafe. This particular test stress tests the localtime() call to
find out whether it is threadsafe. See perlthrtut for more information.

Failure of Thread (5.005-style) tests

Note that support for 5.005-style threading is deprecated,
experimental and practically unsupported. In 5.10, it is expected
to be removed. You should migrate your code to ithreads.

The following tests are known to fail due to fundamental problems in
the 5.005 threading implementation. These are not new failures--Perl
5.005_0x has the same bugs, but didn't have these tests.

../ext/B/t/xref.t 255 65280 14 12 85.71% 3-14

../ext/List/Util/t/first.t 255 65280 7 4 57.14% 2 5-7

../lib/English.t 2 512 54 2 3.70% 2-3

../lib/FileCache.t 5 1 20.00% 5

../lib/Filter/Simple/t/data.t 6 3 50.00% 1-3

../lib/Filter/Simple/t/filter_only. 9 3 33.33% 1-2 5

../lib/Math/BigInt/t/bare_mbf.t 1627 4 0.25% 8 11 1626-1627

../lib/Math/BigInt/t/bigfltpm.t 1629 4 0.25% 10 13 1628-

1629

../lib/Math/BigInt/t/sub_mbf.t 1633 4 0.24% 8 11 1632-1633

../lib/Math/BigInt/t/with_sub.t 1628 4 0.25% 9 12 1627-1628

../lib/Tie/File/t/31_autodefer.t 255 65280 65 32 49.23% 34-65

../lib/autouse.t 10 1 10.00% 4

op/flip.t 15 1 6.67% 15

These failures are unlikely to get fixed as 5.005-style threads
are considered fundamentally broken. (Basically what happens is that
competing threads can corrupt shared global state, one good example
being regular expression engine's state.)

Timing problems

The following tests may fail intermittently because of timing
problems, for example if the system is heavily loaded.

Tied/Magical Array/Hash Elements Do Not Autovivify

For normal arrays $foo = \$bar[1]
will assign undef to
$bar[1]
(assuming that it didn't exist before), but for
tied/magical arrays and hashes such autovivification does not happen
because there is currently no way to catch the reference creation.
The same problem affects slicing over non-existent indices/keys of
a tied/magical array/hash.

Unicode in package/class and subroutine names does not work

One can have Unicode in identifier names, but not in package/class or
subroutine names. While some limited functionality towards this does
exist as of Perl 5.8.0, that is more accidental than designed; use of
Unicode for the said purposes is unsupported.

One reason of this unfinishedness is its (currently) inherent
unportability: since both package names and subroutine names may
need to be mapped to file and directory names, the Unicode capability
of the filesystem becomes important-- and there unfortunately aren't
portable answers.

Platform Specific Problems

AIX

If using the AIX native make command, instead of just "make" issue
"make all". In some setups the former has been known to spuriously
also try to run "make install". Alternatively, you may want to use
GNU make.

In AIX 4.2, Perl extensions that use C++ functions that use statics
may have problems in that the statics are not getting initialized.
In newer AIX releases, this has been solved by linking Perl with
the libC_r library, but unfortunately in AIX 4.2 the said library
has an obscure bug where the various functions related to time
(such as time() and gettimeofday()) return broken values, and
therefore in AIX 4.2 Perl is not linked against libC_r.

vac 5.0.0.0 May Produce Buggy Code For Perl

The AIX C compiler vac version 5.0.0.0 may produce buggy code,
resulting in a few random tests failing when run as part of "make
test", but when the failing tests are run by hand, they succeed.
We suggest upgrading to at least vac version 5.0.1.0, that has been
known to compile Perl correctly. "lslpp -L|grep vac.C" will tell
you the vac version. See README.aix.

If building threaded Perl, you may get compilation warning from pp_sys.c:

This is harmless; it is caused by the getnetbyaddr() and getnetbyaddr_r()
having slightly different types for their first argument.

Alpha systems with old gccs fail several tests

If you see op/pack, op/pat, op/regexp, or ext/Storable tests failing
in a Linux/alpha or *BSD/Alpha, it's probably time to upgrade your gcc.
gccs prior to 2.95.3 are definitely not good enough, and gcc 3.1 may
be even better. (RedHat Linux/alpha with gcc 3.1 reported no problems,
as did Linux 2.4.18 with gcc 2.95.4.) (In Tru64, it is preferable to
use the bundled C compiler.)

AmigaOS

Perl 5.8.0 doesn't build in AmigaOS. It broke at some point during
the ithreads work and we could not find Amiga experts to unbreak the
problems. Perl 5.6.1 still works for AmigaOS (as does the 5.7.2
development release).

Cygwin ndbm tests fail on FAT

One can build but not install (or test the build of) the NDBM_File
on FAT filesystems. Installation (or build) on NTFS works fine.
If one attempts the test on a FAT install (or build) the following
failures are expected:

../ext/NDBM_File/ndbm.t 13 3328 71 59 83.10% 1-2 4 16-71

../ext/ODBM_File/odbm.t 255 65280 ?? ?? % ??

../lib/AnyDBM_File.t 2 512 12 2 16.67% 1 4

../lib/Memoize/t/errors.t 0 139 11 5 45.45% 7-11

../lib/Memoize/t/tie_ndbm.t 13 3328 4 4 100.00% 1-4

run/fresh_perl.t 97 1 1.03% 91

NDBM_File fails and ODBM_File just coredumps.

If you intend to run only on FAT (or if using AnyDBM_File on FAT),
run Configure with the -Ui_ndbm and -Ui_dbm options to prevent
NDBM_File and ODBM_File being built.

DJGPP Failures

t/op/stat............................FAILED at test 29

lib/File/Find/t/find.................FAILED at test 1

lib/File/Find/t/taint................FAILED at test 1

lib/h2xs.............................FAILED at test 15

lib/Pod/t/eol........................FAILED at test 1

lib/Test/Harness/t/strap-analyze.....FAILED at test 8

lib/Test/Harness/t/test-harness......FAILED at test 23

lib/Test/Simple/t/exit...............FAILED at test 1

The above failures are known as of 5.8.0 with native builds with long
filenames, but there are a few more if running under dosemu because of
limitations (and maybe bugs) of dosemu:

t/comp/cpp...........................FAILED at test 3

t/op/inccode.........................(crash)

and a few lib/ExtUtils tests, and several hundred Encode/t/Aliases.t
failures that work fine with long filenames. So you really might
prefer native builds and long filenames.

FreeBSD built with ithreads coredumps reading large directories

This is a known bug in FreeBSD 4.5's readdir_r(), it has been fixed in
FreeBSD 4.6 (see perlfreebsd (README.freebsd)).

FreeBSD Failing locale Test 117 For ISO 8859-15 Locales

The ISO 8859-15 locales may fail the locale test 117 in FreeBSD.
This is caused by the characters \xFF (y with diaeresis) and \xBE
(Y with diaeresis) not behaving correctly when being matched
case-insensitively. Apparently this problem has been fixed in
the latest FreeBSD releases.
( http://www.freebsd.org/cgi/query-pr.cgi?pr=34308 )

IRIX fails ext/List/Util/t/shuffle.t or Digest::MD5

IRIX with MIPSpro 7.3.1.2m or 7.3.1.3m compiler may fail the List::Util
test ext/List/Util/t/shuffle.t by dumping core. This seems to be
a compiler error since if compiled with gcc no core dump ensues, and
no failures have been seen on the said test on any other platform.

Similarly, building the Digest::MD5 extension has been
known to fail with "*** Termination code 139 (bu21)".

The cure is to drop optimization level (Configure -Doptimize=-O2).

HP-UX lib/posix Subtest 9 Fails When LP64-Configured

If perl is configured with -Duse64bitall, the successful result of the
subtest 10 of lib/posix may arrive before the successful result of the
subtest 9, which confuses the test harness so much that it thinks the
subtest 9 failed.

If you are building on a UFS partition, you will also probably see
t/op/stat.t subtest #9 fail. This is caused by Darwin's UFS not
supporting inode change time.

Also the ext/POSIX/t/posix.t subtest #10 fails but it is skipped for
now because the failure is Apple's fault, not Perl's (blocked signals
are lost).

If you Configure with ithreads, ext/threads/t/libc.t will fail. Again,
this is not Perl's fault-- the libc of Mac OS X is not threadsafe
(in this particular test, the localtime() call is found to be
threadunsafe.)

Mac OS X dyld undefined symbols

If after installing Perl 5.8.0 you are getting warnings about missing
symbols, for example

dyld:perlUndefinedsymbols

_perl_sv_2pv

_perl_get_sv

you probably have an old pre-Perl-5.8.0 installation (or parts of one)
in /Library/Perl (the undefined symbols used to exist in pre-5.8.0 Perls).
It seems that for some reason "make install" doesn't always completely
overwrite the files in /Library/Perl. You can move the old Perl
shared library out of the way like this:

cd /Library/Perl/darwin/CORE

mvlibperl.dyliblibperlold.dylib

and then reissue "make install". Note that the above of course is
extremely disruptive for anything using the /usr/local/bin/perl.
If that doesn't help, you may have to try removing all the .bundle
files from beneath /Library/Perl, and again "make install"-ing.

OS/2 Test Failures

The following tests are known to fail on OS/2 (for clarity
only the failures are shown, not the full error messages):

../lib/ExtUtils/t/Mkbootstrap.t 1 256 18 1 5.56% 8

../lib/ExtUtils/t/Packlist.t 1 256 34 1 2.94% 17

../lib/ExtUtils/t/basic.t 1 256 17 1 5.88% 14

lib/os2_process.t 2 512 227 2 0.88% 174 209

lib/os2_process_kid.t 227 2 0.88% 174 209

lib/rx_cmprt.t 255 65280 18 3 16.67% 16-18

op/sprintf tests 91, 129, and 130

The op/sprintf tests 91, 129, and 130 are known to fail on some platforms.
Examples include any platform using sfio, and Compaq/Tandem's NonStop-UX.

Test 91 is known to fail on QNX6 (nto), because sprintf'%e',0
incorrectly produces 0.000000e+0
instead of 0.000000e+00
.

For tests 129 and 130, the failing platforms do not comply with
the ANSI C Standard: lines 19ff on page 134 of ANSI X3.159 1989, to
be exact. (They produce something other than "1" and "-1" when
formatting 0.6 and -0.6 using the printf format "%.0f"; most often,
they produce "0" and "-0".)

The op/pack failure ("Cannot compress negative numbers at op/pack.t line 126")
is serious but as of yet unsolved. It points at some problems with the
signedness handling of the C compiler, as do the 64bitint, arith, and pow
failures. Most of the rest point at problems with SysV IPC.

This is caused by a bug in the awk utility of UNICOS/mk. You can ignore
the error, but it does cause a slight problem: you cannot fully
benefit from the h2ph utility (see h2ph) that can be used to
convert C headers to Perl libraries, mainly used to be able to access
from Perl the constants defined using C preprocessor, cpp. Because of
the above error, parts of the converted headers will be invisible.
Luckily, these days the need for h2ph is rare.

If building Perl with interpreter threads (ithreads), the
getgrent(), getgrnam(), and getgrgid() functions cannot return the
list of the group members due to a bug in the multithreaded support of
UNICOS/mk. What this means is that in list context the functions will
return only three values, not four.

The failures in dumper.t and downgrade.t are problems in the tests,
those in io_unix and sprintf are problems in the USS (UDP sockets and
printf formats). The pat, tr, and fold failures are genuine Perl
problems caused by EBCDIC (and in the pat and fold cases, combining
that with Unicode). The Constant and Embed are probably problems in
the tests (since they test Perl's ability to build extensions, and
that seems to be working reasonably well.)

Unicode Support on EBCDIC Still Spotty

Though mostly working, Unicode support still has problem spots on
EBCDIC platforms. One such known spot are the \p{}
and \P{}
regular expression constructs for code points less than 256: the
pP
are testing for Unicode code points, not knowing about EBCDIC.

Seen In Perl 5.7 But Gone Now

Time::Piece
(previously known as Time::Object
) was removed
because it was felt that it didn't have enough value in it to be a
core module. It is still a useful module, though, and is available
from the CPAN.

Perl 5.8 unfortunately does not build anymore on AmigaOS; this broke
accidentally at some point. Since there are not that many Amiga
developers available, we could not get this fixed and tested in time
for 5.8.0. Perl 5.6.1 still works for AmigaOS (as does the 5.7.2
development release).

The PerlIO::Scalar
and PerlIO::Via
(capitalised) were renamed as
PerlIO::scalar
and PerlIO::via
(all lowercase) just before 5.8.0.
The main rationale was to have all core PerlIO layers to have all
lowercase names. The "plugins" are named as usual, for example
PerlIO::via::QuotedPrint
.

The threads::shared::queue
and threads::shared::semaphore
were
renamed as Thread::Queue
and Thread::Semaphore
just before 5.8.0.
The main rationale was to have thread modules to obey normal naming,
Thread::
(the threads
and threads::shared
themselves are
more pragma-like, they affect compile-time, so they stay lowercase).

Reporting Bugs

If you find what you think is a bug, you might check the articles
recently posted to the comp.lang.perl.misc newsgroup and the perl
bug database at http://bugs.perl.org/ . There may also be
information at http://www.perl.com/ , the Perl Home Page.

If you believe you have an unreported bug, please run the perlbug
program included with your release. Be sure to trim your bug down
to a tiny but sufficient test case. Your bug report, along with the
output of perl -V
, will be sent off to perlbug@perl.org to be
analysed by the Perl porting team.